A probability distribution over latent causes in the orbitofrontal cortex

The orbitofrontal cortex (OFC) has been implicated in both the representation of “state”, in studies of reinforcement learning and decision making, and also in the representation of “schemas”, in studies of episodic memory. Both of these cognitive constructs require a similar inference about the underlying situation or “latent cause” that generates our observations at any given time. The statistically optimal solution to this inference problem is to use Bayes rule to compute a posterior probability distribution over latent causes. To test whether such a posterior probability distribution is represented in the OFC, we tasked human participants with inferring a probability distribution over four possible latent causes, based on their observations. Using fMRI pattern similarity analyses, we found that BOLD activity in OFC is best explained as representing the (log-transformed) posterior distribution over latent causes. Furthermore, this pattern explained OFC activity better than other task-relevant alternatives such as the most probable latent cause, the most recent observation, or the uncertainty over latent causes.